This invention relates generally to gas turbine components, and more particularly to stationary turbine airfoils.
A gas turbine engine includes a compressor that provides pressurized air to a combustor wherein the air is mixed with fuel and ignited for generating hot combustion gases. These gases flow downstream to one or more turbines that extract energy therefrom to power the compressor and provide useful work such as powering an aircraft in flight. In a turbofan engine, which typically includes a fan placed at the front of the core engine, a high pressure turbine powers the compressor of the core engine. A low pressure turbine is disposed downstream from the high pressure turbine for powering the fan. Each turbine stage commonly includes a stationary turbine nozzle followed in turn by a turbine rotor. The turbine nozzle comprises a row of circumferentially side-by-side nozzle segments each including one or more stationary airfoil-shaped vanes mounted between inner and outer band segments or “platforms” for channeling the hot gas stream into the turbine rotor. The turbine rotor comprises a row of circumferentially side-by-side airfoil-shaped blades with arcuate platforms.
It is well known that a vortex flow, referred to as a “horseshoe” vortex because of its shape, occurs around the turbine airfoils (i.e. both blades and vanes) near the inner and outer platforms in vanes and near the inner platform and tip for blades. The strength of the vortex has a direct affect on the airfoil performance, and therefore, the performance of the turbine as a whole. As the vortex strength increases, the performance of the turbine decreases. The performance impact is greatest if the vortex system migrates to the suction side of the airfoil and then up the span towards the middle of the airfoil. Accordingly, there is a need for a turbine airfoil which reduces the strength of the vortex system or inhibits the cross-passage migration of the vortex system.